hella 500 vs. hella 500FF
 

Im gonna start the RAD ROOF RACK build in the morning. O n my roof rack I am planning to put four hellas across the front of it. Today while shopping at WalMart I noticed they have the hella 500's and the hella 500FF's. What one of these should I go with and what is the difference besides six dollars more for the 500FF? Thanks for your help.